1. Field of the Invention
The present invention relates to a backlight module having a light diffusing device and, more particularly, to a device suitable for a direct-type backlight module to uniformly diffuse light rays emanating from a light source.
2. Description of Related Art
In general, a large-sized liquid crystal panel uses a direct-type backlight module to generate light, the direct-type backlight module including a lamp (a light source), a light diffusing plate, a reflecting plate and a frame. The luminance distribution of the backlight module, whether it is uniform or not, depends on the design of the components of the aforesaid direct-type backlight module.
Traditionally, to provide the backlight module with a uniform luminance distribution of light rays, a component such as the light diffusing plate is subject to a dim process, or alternatively, a diffuser film is disposed on the light diffusing plate. However, it causes not only the luminance of the whole backlight module to be reduced but also damages to the diffuser film as a result of heat generated by the lamp. Hence, the distance between the lamp and the light diffusing plate has to be increased. As a result, the thickness of the whole backlight module is increased. Furthermore, a change in the distance between the lamp and the light diffusing plate causes the backlight module to have a non-uniform luminance distribution, impairing the quality of the backlight module.
In addition, another known method for eliminating the aforesaid problems is to have the light diffusing plate screen-printed directly so as to form a plurality of dotted patterns for shielding light on the surface of the light diffusing plate. Thus, the problem of non-uniform luminance distribution caused by the change in the distance between the lamp and the light diffusing plate is solved. However, this still reduces the luminance of the whole backlight module, and needs to be improved.
Therefore, it is desirable to provide an improved backlight module having a light diffusing device to mitigate and/or obviate the aforementioned problems.